Traffic control system

ABSTRACT

A traffic control and warning system for the control of traffic characterized by a series of traffic lights selectively operated through relays which are operated by switches located in the roadway and which switches are tripped by the wheels of a vehicle. Provision is made for warning drivers when a vehicle stalls in the roadway.

United States Patent [191 McGimpsey 1 TRAFFIC CONTROL SYSTEM [76]Inventor: John W. McGimpsey, 83 Oakdene Ave, Teaneck, NJ. 07666 [22]Filed: Dec. 9, 1971 [21] Appl. No.: 206,274

[52] US. Cl 340/31 R [51] Int. Cl G08g l/02 [58] Field of Search 340/31R, 38 R, 35, 340/41, 22,31 A, 38 L [56] References Cited UNITED STATESPATENTS 3,618,003 11/1971 Marshall 340/31 R 3,593,262

7/1971 Spencer .7 340/36 1 Jan. 1, 1974 6/1971 Davin 340/31 R 9/1966Barker 340/31 R Primary Examiner-Kathleen H. Claffy AssistantExaminer-Randall P. Myers Atl0rneyReno A. Del Ben [57] ABSTRACT Atraffic control and warning system for the control of trafficcharacterized by a series of traffic lights selectively operated throughrelays which are operated by switches located in the roadway and whichswitches are tripped by the wheels of a vehicle. Provision is made forwarning drivers when a vehicle stalls in the roadway.

4 C aims 5 Qrewingfi PAIENIEDJAH 1 m4 SHEET 2 BF 3 Eu mm mm um vwINVENTOR W MCGIMPSEY V ATTORNEY PATENIEB 3, 783.446

SHEET 3 OF INVENTOR JOHN W. MCGIMPSEY ATTORNEY TRAFFIC ,CONTROL SYSTEMThis invention dealswith traffic control devices, and in particular withswitching mechanisms for controlling traffic and the speed of trafficalong various portions of a route, with particular emphasis on thecontrol of traffic where vision is obscured, such ,as by.heavy fog.

In the past, it has frequently been necessary on highspeed roads, suchasturnpike s, to close said roads or take other drastic.action.-to;prevent accidents and multiple-car collisions. Variousattemptshave been made to alleviate the fog-conditions, whichattemptshave gone so far as to theinstallation of fans in attempts to blow-offthe fog fromthe roadway. The methods which have'been tried havegenerallybeen ineffective and costly.

The present invention .attempts a solution, of this problem by providinga traffic signal system operated by pads or contact bars: installed inthe roadway along those sections of the roadway persistently troubled byfog problems or other problems of obscured vision, whereby a driver maybe warned when a car is either immediately in front of the driver orelse has stalled on the roadway.

One of the objects of this invention is to provide a warning signalsystem for fogbound roadways whereby traffic can be effectively. andeasily controlled.

Another object of this invention is to providea signal system which willlet a driver known what to do without actually seeing what is ahead ofhim.

Still another object of this inventionis to provide a signal systemwhich will automatically alert adriver to expect an emergency situationahead of him so that the driver can take appropriate action in advance.

Another object of the inventionis to prevent vehicles from riding tooclose together andwarning vehicles when a vehicle is stopped by reasonof a malfunction on fog bound roads.

These and other objects of the invention will appear from time to timeas these specifications proceed and with reference to the accompanyingdrawings, wherein:

F IG. 1 is a view of a typical road interchange, showing a portion ofthe invention in place.

FIG. 2 is a plan view of a contact bar assembly, part of the invention.

FIG. 3 is a cross-sectional view. of the contact bar assembly of FIG. 2,taken on the plane 3-3 ofFIG. 2.

F IG. .4 is a schematic diagram of a portion of the wiring circuitry ofthe invention; indicating. the various relays of the invention andtheconnections thereto.

FIG. 4A is a schematic diagram of a. portion of the wiring circuitry ofthe invention, and is an extension of the schematic diagramof FlG.,4,linesnumbered 11 through 37 of FIG. 4A 1 being continuationsrespectively, of lines numbered ll through 37 ofsFlG...4, and indicatingthe connections of the various relays to stop lights and road contactbars.

Referring to the drawings in-which the same numerals are used for theidentical or similar parts in the various drawings:

Generally the inventionisdesigned primarily to provide a warning signalsystem for fogbound turnpikes and thruways, and for this purpose contactbar assemblies, 100, are installedin the roadway and include electricalcontacts for controlling relays which control spotlights.

The contact bar assemblies, designated generally by the numeral 100,typically comprise a contact bar,.l01,

which installed substantially level with a roadway, springs, 102,installedin a cavity .103 in the roadbed under the contact bar 101 andwhich support the contact bar, mating rigid supportsil04 provided on thecontact bar 101 and in the cavity .103, which will support the contactbar 101 whenthe springs 102 have been depressed a predetermined distanceand at least one momentary contact switch installed in the cavity 103and operated by the depression of the contact bar 101. There are twotypes of momentary contact switches 105 a momentary open, normallyclosed momentary contact switch, 109, anda momentary close, normallyopen momentary contact switch, 110. A momentary close, normally openmomentary contact switch, 110, comprises at leasttwo electrical contacts.106 installed in the cavity 103 and attached by suitable .less than themating portions of the rigid supports 104 so that depressing the contactbar 101 will cause the bus bar 107 to make contact .with the electricalcontacts 106, closing one and opening the other circuit between theelectrical contacts 106. A momentary open, normally closed momentarycontact switch, 109, comprises at least two electrical contacts 111installed in the cavity 103 and attached by suitable leads to thevarious relays of the invention and a bus bar 107 supported on springs108. The ends of the electrical contacts 111 are formed so that theyextend above. the bus bar 107 and make contact with same wherethecontact bar 101 is not depressed. The bus bar 107 is supported in such amanner that. it will break contact with the electrical contacts 111 whenthe contact bar 101 is depressed.

In the various drawings, specific contact bar assemblies and theirvarious parts are designated by the numerals 117, 118, 119, 120,121,122, 123, and 124.

cle, a momentary contact switch in the contact bar assembly is closedand energizes a relay which puts on a red light at the stationassociated with this contact. bar

assembly and at the same time breaking contactfor a red light at theprevious station and putting on a green light at this previous station.These stations can be spaced apart according to the best safety rules.

The only way a red light willgo off .is by a vehicle depressing acontact bar on the road at the next station ahead of this red light.When this happens this red light changes to a green light allowingtraffic to move to the next station.

According to this system, all .vehicles would be spaced equally farapart unless a vehicle would choose to go past a red light. If allvehicles travel at the same speed each light will go, green asthevarious vehicles reach contact bars. If, on the otherhand, the speedsare different, the red lights will-stop traffic, being controlled by thespeed of thevehiclle that is ahead. The system can be turned on whenfogappears, and can be shut off during periods of normal visibility. Anaudible signal can be installed in conjunction with the visible signals.

When a light does not change from red to green within a specified periodof time such as would occur when a vehicle became disabled, a time delayswitch which is incorporated in the circuitry changes the red light to ablinker light, thereby allowing traffic to proceed while warning of apossible obstruction ahead. A manual reset is provided to put the systemback into normal operation when the obstruction has been eliminated.

At a section of roadway which includes an intersection a contact barassembly No. 118 is installed at a predetermined distance from a sideroad entry and when a vehicle on the main road depresses the contact bar101 of contact bar assembly No. 118 in the main road the side road redlight is put on, stopping side road traffic.

When a vehicle on the main road hits the contact bar 101 of contact barassembly No. 119 at the intersection, it will cancel this red light 168and put a green light 162 on the preceding station and a red light 168on the side road, and it also puts red light 164 on.

When a vehicle approaches the main road from the side road it willdepress the contact bar 101 of contact bar assembly No. 122, energizingby-pass relay No. 61, and will prevent the main road red light No. 164from going off due to a vehicle on the main road depressing contact bar101 of contact bar assembly No. 120. At the same time the side road redlight 168 will go off and the side road green light 170 will go on,allowing the vehicle on the side road to enter the main road. The sideroad vehicle then passes over the stop line, which is located betweencontact bar assemblies No. 122 and No. 123, and will depress bar 101 ofcontact bar assembly 123, and in so doing cuts the power to coil ofbypass relay No. 61. The vehicle entering then proceeds to contact barassembly No. 124 which, when its contact bar 101 is depressed, will puton red light 164 and 168.

When the vehicle leaves the main road to get off on side road it willdepress the contact bar 101 of contact bar assembly 121 on the side roadwhich will cancel red light 160 and put on green light 162 at thepreceding station.

Referring now to FIGS. 4 and 4A, switch No. 52 and No. 62 are time delayrelay switches. Switches No. 56 and No. 66 are normally closedpush-button switches which can be momentarily opened to reset certainrelays, as hereinafter indicated.

Relays No. 51, 57, 58, 59, 60, and 61 are double pole double throwrelays, having respectively, terminals 511 and 512, 571, and 572, 581and 582, 591 and 592, 601 and 602, 611 and 612 connected to the oppositesides of their respective coils. The contact bar, 150, of eachrespective relay is in the position where the conductors of therespective contact 'bar makes contact, respectively with terminals 513and 514, 573 and 574, 583 and 584, 593 and 594, 603 and 604, and 613 and614, of the respective relay with which the contact bar is associatedwhen the respective coil is not energized.

Relays N0. 53, 54, 63 and 64 are double pole-single throw relays of thenormally closed circuit type, having, respectively, terminals 531 and532, 541 and 542, 631 and 632, and 641 and 642 connected to oppositesides of their respective coils. The contact bars, 150, of the relaysare positioned so that they make contact, respectively, with terminals533 and 534, 543 and 544, 633 and 634, and 643 and 644 when the coil isnot energized.

Relays No. 55 and 65 are double-pole single throw relays of the normallyopen circuit type, having, respectively, terminals 551 and 552, and 651and 652 connected to opposite sides of their respective coils. Thecontact bars, 150, of the relays are positioned so that they do not makecontact, respectively, with terminals 555 and 556, and 655 and 656, whenthe coil is not energized.

Lines designated L1 and L2 are opposite sides of a source of electricalpower, the side designated L1 being preferably the ground side, whilethe side designated L2 is preferably the hot side.

The operation of the relays is as follows:

When the contact bar 101 of the contact bar assembly No. 117 in the mainroad is depressed by the weight of a vehicle the normally open momentarycontact switch 109 of contact bar assembly 117 is closed allowingcurrent to flow from power line L2 to the normally closed momentarycontact switch 109 in contact bar assembly 121 and then to one of thenormally closed momentary contact switch 109 in contact bar assembly 119and then to the normally closed push button station 56 and then throughto one side of relay 5] energizing the coil of relay 51. The movablecontact bar of the relay of which the two poles are connected to powerlines 61 and 62 respectively through terminals 515 and 516, are put incontact by the energized coil with the two terminals 517 and 518allowing current to flow in the red light and allowing current to flowin time delay relay 52. In the event that the vehicle does not reachcontact bar assembly 119 due to a malfunction, at a set time the timedelay relay 52 will energize the coil of relay 53 causing thecancellation of the main road red light 160 and cancelling relay 54.When relay 54 is not energized the time delay switch puts current intothe blinker light flasher 163 which in turn causes the yellow light 161to flash continuously. The blinker light flasher 163 will stay on untilcancelled by opening the normally closed push button switch 56, whichwill also cause the red and green lights to operate in a normal mode.Relay 55 which is also energized by time delay relay 52 by-passesnormally closed momentary contact switch 109 of the Contact bar assembly119 preventing the opening of this circuit and putting on green light162 while the blinker light flasher is in service.

When the vehicle does not have a malfunction it will continue on tocontact bar assembly 118 closing switch 110 of bar assembly 118. Currentfrom power line L2 will go through said switch 110 of contact barassembly 118 and then through the normally closed momentary contactswitch 109 of contact bar assembly 119 to terminal 572 of relay 57energizing the coil and putting on side road red light 168. When thevehicle depresses bar 101 of contact bar assembly 119 it will openmomentary contact switch 109 coming from the contact bar assembly 118circuit, cancelling current relay 57 and cutting off power to side roadred light 168. The normally closed momentary contact switch 109 ofcontact bar assembly 119 coming from the contact bar assembly 121circuit will open, cancelling current to terminal 512 of the coil ofrelay 51 which relay 51 will cancel red light 160 at contact barassembly 117, cutting power to time delay relay 52 which cancels relay53, relay 54 and relay 55. Green light 162 will be on at bar 117 whenrelay 51 is not energized.

The normally open momentary contact switch 110 of contact bar assembly119 when depressed will close, allowing current to flow through thenormally closed momentary contact switch 109 of contact bar assembly 120to terminals 642 and 646 of relay 64 to terminal 602 of relay 60,putting on side road red light 168, to terminal 582 of relay 58, puttingcontact bar 150 of relay 58 in contact with the terminals of relay 58which puts on red light at bar 119 and puts time delay relay 62 inservice. This circuit from normally open momentary contact switch 110 ofcontact bar assembly 119 also permits current to flow through the L2line side of relay 59 which cancels side road green light 170. Relays 53and 55 which are maintaining circuits are supplied power by time delayrelay 52. Relays 63, 64, and 65 are supplied power bytime delay relay62. When a vehicle reaches contact bar assembly 120 a normally closedmomentary contact switch 109 will open, cutting power to relays 58, 59,and 60, putting on green lights 166 on main road and 170 on side roadentry. When a vehicle coming from side road entry depresses bar 101 ofcontact bar assembly 122 the normally open momentary contact switch 110closes allowing current to flow through the normally closed momentarycontact switch 109 of contact bar assembly 123 to terminal 612 of relay61, which bypasses normally closed momentary contact switch 109 atcontact bar assembly 120 preventing opening of circuit when contact bar101 of contact bar assembly 120 is depressed, so that red light 164 andgreen light 170 will remain on allowing side road vehicle to proceed onto main road. If a vehicle fails to reach contact bar assembly 120 dueto malfunction the time delay relay 62 at a set time will allow currentto flow into terminal 652 of relay 65 permitting bypassing of thenormally closed momentary contact switch 109 of contact bar assembly 120preventing green lights 166 and 170 from coming on. At the same timerelay 62 will allow current to flow into terminals 632 of relay 63energizingthe coil. Relay 62 when energized will open the circuit to themain road red light 164 and open circuit to relay 64 putting on blinkerlight flashers 167 and 171 which will cause yellow lights 165 and 169respectively to flash continuously. When the disabled vehicle isremoved, a nor mally closed push button 66 is provided which can bepushed, cancelling blinker light flashers 167 and 171 and putting redand green light system into normal ser vice again.

When a vehicle chooses to exit at a side road it will depress a contactbar in the exit road such as contact bar 101 of contract bar assembly121, which will open circuit from switch 110 of contract bar assembly117 to switch 109 of contact bar assembly 119 cancelling current torelay 51 and putting on green light 162 at contact bar assembly 117.

The switch 110 of contact bar assembly 120 is connected to thesubsequent contact bar assembly which is identical to contact barassembly 117. The switch 109 of contact bar assembly 117 is connected toa switch similar to switch .110 of contact bar assembly 120, in thepreceding contact bar assembly. In this i and so on to the otherpreceding stations, putting all these stations on blinker lightsassuming that all these stations are on red lights. If any are on greenlights there is no problem. To avoid this the time setting can bearranged so that there would be a difference of a few seconds betweeneach station. This could be done in groups of five or ten stations sothat there would not be too long a time delay between a large group ofstations.

The time delay relays may be wired to a monitored centrally locatedindicator panel, wired in parallel with the various yellow lights, toaid authorities in determining the location of possible problems intraffic.

Considering now the operation of the system during its different phases:

When there is no traffic in a typical stage or approaching the stagefrom the immediately preceding stage, the coils of the various relaysare not energized, and electrical current flows from line L2 to terminal516, thence to terminal 514, along line 17 to green light 162,illuminating same, thence along line 14 to terminal 513, thence toterminal 515 which is grounded to line L1. At the same time electricalcurrent flows from line L2 to terminal 596, thence to terminal 594, thenalong line 21 to green light 170, illuminating same, thence along line27 to terminal 573 thence to terminal 575 thence to terminal 593, thenceto terminal 595 which is grounded to line L1. At the same timeelectrical current flows from line L2 to terminal 586 thence to terminal584 thence along line 29 to green light 166, illuminating same, thencealong line 22 to terminal 582 thence to terminal 585 which is groundedto line Ll, thus all traffic lights are green in the particular stage.

When a car approaches the stage, it passes over contact bar assembly 117causing switch of contact bar assembly 117 to momentarily close,resulting in electrical power from line L2 flowing from terminal 516along line 16, through switch 110 of contact bar assembly 117 to switch109 of contact bar assembly 121, thence to switch 109 of contact barassembly 119, thence along line 19 to terminal 553 thence to switch 56thence to terminal 512, energizing the coil of relay 51, thence toterminal 542 and terminal 546. At the same time power flows fromterminal 553 to terminal 555 and along line 18 to switch 109 of contactbar assembly 121, resulting in the coil of relay 5] being keptenergized. The energizing of relay 51 starts the timer 52, sinceelectrical power now flows from terminal 516 to terminal 518 and then totimer 52. The power flowing out of terminal 518 also flows to terminal534, thence to terminal 536 and to red light 160, energizing sameimmediately behind the car passing over contact bar assembly 117, thenceto terminal 517, thence to terminal 515 which is groundedto line L1. Atthe same time relay 54 is energized, since terminal 541 is groundedthrough terminals 533, 534, and 517. If the car does not proceed to oneof the next contact bar assemblies, the timer will, after apredetermined time interval, energize the coils of relays 53 and 54,breaking the connections to red light 160, and de-energizing relay 54,causing electrical powerfrom terminal 546 to flow to terminal 544,thence along line 15 to blinker flasher 163, which will sendintermittent power to yellow light 161, energizing same, which blinkerflasher 163 and yellow light 161 are grounded by means of line 11, andterminals 543, 517, and 51:5 to line L1.

If the car exits at the ramp, it will pass over contact bar 121,breaking the electrical connection through switch 109 of contact bar121, which will result in the breaking of the electrical connection tothe coil of relay 51, causing electrical power to flow from line L2through terminal 516, thence to terminal 514, then along line 17 togreen light 162, energizing same, thence along line 14 to terminal 513,thence to terminal 515 which is grounded to line L1, and at the sametime de-energizing either light 160 or light 161, whichever wasenergized in the manner previously indicated.

If, instead of exiting, the car continues to contact bar assembly 118,it will momentarily close switch 110 of contact bar assembly 118. Thiswill cause electrical power to flow from line L2, through switch 110 ofcontact bar assembly 118, through switch 109 of contact bar assembly 119which is connected to switch 110 of contact bar assembly 118, along line26 to terminal 572, energizing the coil of relay 57 and causingelectrical power to flow from line L2 along line 31 to red light 168,illuminating same, thence along line 30 to terminal 577, thence toterminal 575 which is connected to terminal 593 and which is grounded toline Ll through terminal 595, at the same time stopping the flow ofelectrical power to green light 170. As the car continues, it will passover contact bar assembly 119, momentarily opening switch 109 andclosing switch 110, allowing electrical power to flow from line L2 alongline 20, through switch 110 of contact bar assembly 119, along line 28and line 35 to switch 109 of contact bar assembly 120, along line 37 toterminals 602 and 582, energizing the coils of relays 60 and 58. Thisallows electrical power to flow from line L2 through terminal 606,through terminal 608 to terminal 634 to red light 164, illuminating samedirectly behind the car, then along line 24 to terminal 636 which is notconnected electrically to terminal 634, then to terminal 608 which isgrounded through terminal 606 to line L2. At the same time electricalpower flows from line L2, along line 31 to red light 168, illuminatingsame, then along line 30 to terminal 607 which is now connectedelectrically to grounded terminal 605. At the same time the flow ofelectrical power to green lights 166 and 170 is interrupted. Meanwhilethe electrical power which had been flowing through switch 109 ofcontact bar assembly 119 has been momentarily interrupted, causing thecoil of relay 51 to be de-energized, resulting in the flow of electricalpower from line L2 through terminal 516, then to terminal 514, alongline 17 to green light 162, illuminating same, then along line 14through terminal 513, to grounded terminal 515, at the same timeinterrupting the flow of electrical power to red light 160. As the carcontinues it will pass over contact bar assembly 120, momentarilyopening switch 109 of contact bar assembly 120. This interrupts the flowof electrical power which comes from line L2 through terminals 596, thenthrough terminal 598, through push button switch 66 to contact barassembly 120, and thus de-energizing the coils of relays 58 and 59,resulting in electrical power flowing from line L2 through terminal 586,then through terminal 584, along line 29 to green light 166,illuminating same, then along line 22, through terminal 582, thenthrough terminal 585 to ground line Ll, while at the same timeelectrical power flows from line L2 by way of terminal 596, thenterminal 594, then line 21 to green light 170, illuminating same, thenalong line 27, then terminal 573, then terminal 575, then terminal 593to terminal 595 which is grounded, and at the same time the flow ofelectrical power to red lights 164 and 168 is interrupted.

If a car approaches the main highway from the entry ramp, it will firstpass over contact bar assembly 122,

momentarily closing switch of contact bar assembly 122. This will causeelectrical power to flow momentarily from line L2 along line 20 throughswitch 110 of contact bar assembly 122 to switch 109 of contact barassembly 123 and along line 33 to terminal 612 energizing the coil ofrelay 61 and causing contacts 615 and 617 to be electrically connectedand contacts 616 and 618 to be electrically connected through the busbar of relay 61 and locked in place by the flow of electrical power fromline L2 through terminal 616, then through terminal 618, along line 32through switch 109 of contact bar assembly 123, along line 33 toterminal 612 of the coil of relay 61, the other terminal 611 of the coilof relay 61 being grounded to line Ll. When the car reaches contact barassembly 123, switch 109 of contact bar assembly 123 is momentarilyopened breaking the circuit through the coil of relay 61 andde-energizing same. When the car reaches contact bar assembly 124 itmomentarily closes switch 110 of contact bar assembly 124 causing acircuit to be made from line L2 through switch 110 of contact barassembly 124, along line 28, through switch 66, through terminal 598, toterminal 596, and back to line L2, and causes electrical power to flowfrom said circuit at switch 66, along line 35 through switch 109 ofcontact bar assembly to terminals 582 and 592, energizing the coils ofrelays 58 and 59, and causing electrical current to flow from lineL2-through terminal 586, through terminal 588, through time delay switch62 to terminal 632, energizing the coil of relay 63, back through theground side of time delay switch 62, to terminal 587 and then toterminal 585, which is grounded. This allows electrical current to flowfrom line L2 through red light 168, illuminating same directly behindthe car, along line 30 to terminal 577, then to terminal 593, then toterminal 595, and then to ground line L1. At the same time electricalcurrent flows from line L2 through terminal 596, through terminal 598,through terminal 634, through terminal 636 to red light 164,illuminating same, then back to ground along line 25, terminal 587 andterminal 585. Simultaneously, electrical power to green lights 166 andis interrupted.

When the vehicle reaches contact bar assembly 120, red lights 164 and168 are extinguished and green lights 166 and 170 are illuminated aspreviously indicated.

The foregoing is a typical illustration of the flow of electricitythrough different portions of the circuits during various phases ofoperation of the invention.

1 claim:

1. A traffic control system, for use in controlling traffic travelingalong a uni-directional roadway having separate entrances and exits,comprising a series of traffic control zones, each of said zonescomprising:

at least one entering detector for sensing the entrance of a vehicleinto the zone; at least one exiting detector for sensing the exiting ofa vehicle from the zone;

at least one traffic signal installed at the entrance to said zone andat each entrance to the said roadway to control traffic travelling alongsaid roadway and entering onto said roadway; each of said trafficsignals being provided with a plurality of differently colored lights;

light controlling switch means operated by said entering and exitingdetectors to control the lighting of said differently colored lights,said entering and exiting detectors being connected to said lightcontrolling switch means in such a manner as to control the lighting ofthe various lights located at the entrances to the zone and to thepreceding zone, so that when a vehicle is detected entering the zone byan entering detector, its presence within the zone is indicated at theentrances to the zone, and when the vehicle is detected leaving the zoneby an exiting detector, itsabsence from the zone is indicated at eachentrance to the zone; and

timing means operating in conjunction with said light controlling switchmeans to activate lights at each entrance to a zone 'to indicate when apossible obstruction in the form of a stopped vehicle may be expected inthe zone, said timing means being adapted to transmit a signal toactivate warning lights at the entrances to a zone when a vehicle in thezone fails to pass from an entering detector to an exiting detector ofthe zone within a predetermined interval of time; and

an entering detector being provided at each entrance to the roadway tosense the approach of a vehicle at an entrance to the roadway and thetraffic control system being adapted to control the same entry of thevehicle onto the roadway and to cause the lights at the entrances to thezone to indicate that the entering vehicle is in the zone associatedwith the roadway entrance.

2. A traffic control system as claimed in claim 1 wherein the enteringdetectors and the exiting detectors comprise pressure operated switchingmeans which comprise a plurality of contact bar assemblies installed incavities in said roadway and at the entrances and exits to said roadway,each of said contact bar assemblies comprising a contact bar mountedsubstantially level with the surface of the roadway and perpendicularlymovable with respect to said surface of the roadway, rigid supports forlimiting said perpendicular movement of said contact bar, spring meansfor supporting said contact bar substantially level with the roadwaywhen there is no stress placed on said contact bar, and momentarycontact switch means operated by the said perpendicular movement of saidcontact bar.

3. A traffic control system as; claimed in claim 1 wherein the lightcontrolling switch means to control the delivery of electrical power tosaid lights comprises

1. A traffic control system, for use in controlling traffic travelingalong a uni-directional roadway having separate entrances and exits,comprising a series of traffic control zones, each of said zonescomprising: at least one entering detector for sensing the entrance of avehicle into the zone; at least one exiting detector for sensing theexiting of a vehicle from the zone; at least one traffic signalinstalled at the entrance to said zone and at each entrance to the saidroadway to control traffic travelling along said roadway and enteringonto said roadway; each of said traffic signals being provided with aplurality of differently colored lights; light controlling switch meansoperated by said entering and exiting detectors to control the lightingof said differently colored lights, said entering and exiting detectorsbeing connected to said light controlling switch means in such a manneras to control the lighting of the various lights located at theentrances to the zone and to the preceding zone, so that when a vehicleis detected entering the zone by an entering detector, its presencewithin the zone is indicated at the entrances to the zone, and when thevehicle is detected leaving the zone by an exiting detector, its absencefrom the zone is indicated at each entrance to the zone; and timingmeans operating in conjunction with said light controlling switch meansto activate lights at each entrance to a zone to indicate when apossible obstruction in the form of a stopped vehicle may be expected inthe zone, said timing means being adapted to transmit a signal toactivate warning lights at the entrances to a zone when a vehicle in thezone fails to pass from an entering detector to an exiting detector ofthe zone within a predetermined interval of time; and an enteringdetector being provided at each entrance to the roadway to sense theapproach of a vehicle at an entrance to the roadway and the trafficcontrol system being adapted to control the same entry of the vehicleonto the roadway and to cause the lights at the entrances to the zone toindicate that the entering vehicle is in the zone associated with theroadway entrance.
 2. A traffic control system as claimed in claim 1wherein the entering detectors and the exiting detectors comprisepressure operated switching means which comprise a plurality of contactbar assemblies installed in cavities in said roadway and at theentrances and exits to said roadway, each of said contact bar assembliescomprising a contact bar mounted substantially level with the surface ofthe roadway and perpendicularly movable with respect to said surface ofthe roadway, rigid supports for limiting said perpendicular movement ofsaid contact bar, spring means for supporting said contact barsubstantially level with the roadway when there is no stress placed onsaid contact bar, and momentary contact switch means operated by thesaid perpendicular movement of said contact bar.
 3. A traffic controlsystem as claimed in claim 1 wherein the light controlling switch meansto control the delivery of electrical power to said lights comprises aplurality of relays wired to said entering and exiting detectors.
 4. Atraffic control system as claimed in claim 1 wherein a flasher isprovided which is operated by said timing means, which flasher provideselectrical power to intermittently operate the lights used to warn abouta possible obstruction, and manually operated reset means are providedwhich are adapted to by-pass the said timing means and to terminate theoperation of the said warning lights.